Untangling a knot of galaxy clusters

Astronomers have captured a spectacular, ongoing collision between a minimum of three galaxy clusters. Knowledge from NASA’s Chandra X-ray Observatory, ESA’s (European House Company’s) XMM-Newton, and a trio of radio telescopes helps astronomers kind out what is going on on this jumbled scene. Collisions and mergers like this are the primary method that galaxy clusters can develop into the large cosmic edifices seen in the present day. These additionally act as the most important particle accelerators within the universe.

The enormous galaxy cluster forming from this collision is Abell 2256, situated 780 million light-years from Earth. This composite picture of Abell 2256 combines X-rays from Chandra and XMM in blue with radio knowledge collected by the Big Metrewave Radio Telescope (GMRT), the Low Frequency Array (LOFAR), and the Karl G. Jansky Very Giant Array (VLA) all in purple, plus optical and infrared knowledge from Pan-STARRs in white and pale yellow.

Astronomers learning this object are attempting to tease out what has led to this unusual-looking construction. Every telescope tells a unique a part of the story. Galaxy clusters are a number of the largest objects within the universe containing tons of and even hundreds of particular person galaxies. As well as, they include monumental reservoirs of superheated gasoline, with temperatures of a number of million levels Fahrenheit. Solely X-ray telescopes like Chandra and XMM can see this scorching gasoline.

The radio emission on this system arises from an much more complicated set of sources. The primary are the galaxies themselves, during which the radio sign is generated by particles blasting away in jets from supermassive black holes at their facilities. These jets are both taking pictures into house in straight and slim traces (these labeled “C” and “I” within the annotated picture, utilizing the astronomer’s naming system) or slowed down because the jets work together with gasoline they’re working into, creating complicated shapes and filaments (“A”, “B,” and “F”). Supply F comprises three sources, all created by a black gap in a galaxy aligning with the left-most supply of this trio.

Radio waves are additionally coming from big filamentary constructions (labeled “relic”), largely situated to the north of the radio-emitting galaxies, possible generated when the collision created shock waves and accelerated particles within the gasoline throughout over two million light-years. A paper analyzing this construction was revealed earlier this yr by Kamlesh Rajpurohit from the College of Bologna in Italy within the March 2022 problem of The Astrophysical Journal. That is Paper I in an ongoing sequence learning totally different points of this colliding galaxy cluster system.

Lastly, there’s a “halo” of radio emission situated close to the middle of the collision. As a result of this halo overlaps with the X-ray emission and is dimmer than the filamentary construction and the galaxies, one other radio picture has been produced to emphasise the faint radio emission. Paper II led by Rajpurohit, just lately revealed within the journal Astronomy and Astrophysics, presents a mannequin that the halo emission could also be attributable to the reacceleration of particles by speedy modifications within the temperature and density of the gasoline because the collision and merging of the clusters proceed. This mannequin, nonetheless, is unable to elucidate all of the options of the radio knowledge, highlighting the necessity for extra theoretical research of this and related objects.